1. Field of the Invention
The present invention relates to a pre-pit signal detecting apparatus, which detects a pre-pit when recording record information, if various record control information required for recording the record information is recorded on a WO (Write Once) type record medium (hereafter, it is referred to as a xe2x80x9cDVD-R (DVD-Recordable)xe2x80x9d) or a random access type record medium (hereafter, it is referred to as a xe2x80x9cDVD-R/W (DVD-Read/Write)xe2x80x9d) where a plurality of recording/reproducing operations are possible, among high dense record media represented by the DVD, whose record density is drastically improved over a conventional CD (Compact Disk) and the like, by forming the pre-pit as pre-information. The present invention also relates to an information recording apparatus which has the pre-pit signal detecting apparatus and records the record information to be primarily recorded.
2. Description of the Related Art
For example, a synchronization signal, address information required for searching a position when recording the record information to be recorded such as video information, rotation control information used for the rotation control of the record medium, clock information to generate a record clock signal used when recording the record information onto the record medium and so on are recorded as the above-mentioned record control information (hereafter, the record control information is abbreviated and referred to as xe2x80x9cpre-informationxe2x80x9d) in many cases.
As a manner of actually recording the pre-information on the record medium, the rotation control information, the clock information and the like are recorded in many cases by wobbling so-called groove tracks or land tracks and thereby correlating the wobbling cycle (period) thereof with the rotation control information, the clock information and the like.
On the other hand, the address information, the synchronization signal and the like are typically recorded by forming pre-pits (i.e., pre-pits formed on a track (for example, the land track) formed between a plurality of turns of the track (for example, it is the groove track, which is wobbled at the wobbling frequency) on which the record information in the record medium is recorded) at an interval synchronous to the wobbling cycle on the record medium in advance.
In case of recording the record information onto the record medium, it is necessary to accurately detect each pre-information, in order to accurately record the record information.
Here, in the information recording apparatus, when respectively detecting the pre-information, the respective pre-information is detected by (i) obtaining a composite signal in which an impulse signal (hereafter, referred to as a pre-pit signal) corresponding to the pre-pit is superimposed on a cyclic signal (hereafter, referred to as a wobbling signal) having a cycle corresponding to the wobbling on the basis of a reflection light of a record light beam, which is irradiated onto each track on the record medium (the reason why such a composite signal is detected is that the pre-pit is formed as a phase pit on a land track adjacent to a wobbled groove track, and then the record light beam is simultaneously irradiated onto the groove track and the phase pit), and (ii) then separating the rotation control information, the clock information and the like which are recorded through the wobbling, and the address information, the synchronization signal and the like which are recorded through the pre-pit, from the composite signal.
More actually, in case of detecting the wobbling signal from the composite signal, the composite signal is passed through a band pass filter in which a frequency of the wobbling signal is used as a central frequency, and accordingly the wobbling signal is extracted.
Also, in case of detecting the pre-pit signal from the composite signal, a gate signal, which has a phase synchronous with that of the extracted wobbling signal and also includes a timing at which the pre-pit is present, is generated to then extract a part of the composite signal (i.e., a part in which the pre-pit signal is included) through this gate signal and further detect the pre-pit signal from this extracted signal.
At this time, in case of generating the gate signal, in order to make the phase thereof synchronous with the extracted wobbling signal, it is necessary to frequency-divide a record clock signal synchronous with a moving speed of the record medium to thereby generate the gate signal.
In this case, a so-called PLL (Phase Locked Loop) circuit is required for generating the gate signal.
However, typically in the band pass filter and the PLL circuit (especially, a phase comparator usually contained in the PLL circuit), phase delays are respectively induced in signals passed through them because of operational performances.
Thus, the gate signal, which is passed through the band pass filter and the phase comparator and is generated from the composite signal in accordance with the above-mentioned procedure, has a problem that a duration while the gate signal is at a xe2x80x9cHIGHxe2x80x9d level may not agree with the timing in which the pre-pit signal in the composite signal is included, because of the phase delay.
Hence, in this case, the pre-pit signal cannot be detected even if using the gate signal.
Moreover, a variation of a characteristic of each member constituting the band pass filter and the PLL circuit (i.e., a deviation from a nominal value), a difference of a temperature characteristic and the like may cause the phase delay to be changed for each information recording apparatus or for each environment where the recording operation is carried out. In this case, the duration while the gate signal is at the xe2x80x9cHIGHxe2x80x9d level and the timing in which the pre-pit is included are further deviated or shifted from each other.
So, in order to cancel this deviation between the gate signal and the pre-pit signal and accurately detect the pre-pit signal, a pulse width of the gate signal (i.e., the duration while the gate signal is at the xe2x80x9cHIGHxe2x80x9d level) may be set to be longer to some degree, and accordingly the duration while the gate signal is at the xe2x80x9cHIGHxe2x80x9d level and the timing in which the pre-pit is included are made coincident with each other.
However, in the actual information recording apparatus, various noises other than the pre-pit signal are typically mixed into the above-mentioned composite signal.
Thus, this case has a problem that, if the pulse width of the gate signal is made wider as mentioned above, the noises are also extracted, and conversely the pre-pit signal cannot be accurately detected.
In other words, in order to detect the pre-pit signal having a predetermined phase relation with the wobbling signal at a high precision (namely, without detecting other noises and the like), it is necessary to make the pulse width of the gate signal used for the detection as narrow as possible. However, the above mentioned method cannot make the pulse width sufficiently narrow because of the above mentioned phase delay.
The present invention is proposed in view of the above mentioned problems. It is therefore an object of the present invention to provide a pre-pit signal detecting apparatus, which can detect the above-mentioned pre-pit signal precisely and accurately among the respective signals corresponding to the above-mentioned pre-information, and an information recording apparatus which includes the pre-pit signal detecting apparatus.
The above object of the present invention can be achieved by a first pre-pit signal detecting apparatus, which is used in an information recording apparatus for recording record information onto a record medium such as a DVD-R etc., on which record control information for controlling a recording operation of the information recording apparatus is recorded in advance by forming a pre-pit on the record medium, for detecting a pre-pit signal corresponding to the pre-pit when the information recording apparatus records the record information onto the record medium. The first pre-pit signal detecting apparatus is provided with: an extracting device such as a band pass filter etc., to which a reproduction signal of the record medium is inputted, for extracting and outputting a predetermined signal component, which is used for detecting the pre-pit signal, out of the inputted reproduction signal; an input controlling device such as a CPU etc., for inputting a standard signal, which is set in advance, to the extracting device in place of the reproduction signal before the pre-pit signal is detected and inputting the reproduction signal to the extracting device when the pre-pit signal is detected; a phase difference detecting device such as a delay amount measuring device etc., for comparing the standard signal outputted by the extracting device with the standard signal inputted by the input controlling device, and for detecting a phase difference generated between the compared standard signals due to an extracting operation of the extracting device before the pre-pit signal is detected; and a pre-pit detecting device such as a delay circuit etc., for detecting the pre-pit signal on the basis of the extracted predetermined signal component while canceling the detected phase difference.
According to the first pre-pit signal detecting device, since the phase difference generated in the extracting device used for the detection of the pre-pit signal is detected in advance and then the actual detection of the pre-pit signal is performed while canceling this detected phase difference, it is possible to accurately detect the pre-pit signal.
In one aspect of the first pre-pit signal detecting apparatus, the extracting device is provided with: a filtering device such as a band pass filter etc., for extracting a partial signal including the pre-pit signal from the reproduction signal, which is generated in response to a reflection light of a recording light beam irradiated onto the record medium; and a gate signal generating device such as a PLL (Phase Lock Loop) circuit etc., for generating a gate signal to extract the pre-pit signal from the extracted partial signal.
According to this aspect, by canceling the phase difference generated in the filtering device and the gate signal generating device, it is possible to accurately detect the pre-pit signal.
In this aspect, the pre-pit detecting device may be provided with a phase controlling device for controlling a phase of the extracted partial signal so as to cancel the detected phase difference and then outputting it to the gate signal generating device.
By this, it is possible to certainly cancel the phase difference.
The above object of the present invention can be also achieved by a second pre-pit signal detecting apparatus, which is used in an information recording apparatus for recording record information onto a record medium such as a DVD-R etc., on which record control information for controlling a recording operation of the information recording apparatus is recorded in advance by forming a pre-pit and a wobbling track having a phase corresponding to the pre-pit on the record medium, for detecting a pre-pit signal corresponding to the pre-pit from a reproduction signal corresponding to a reflection light of a recording light beam irradiated onto the record medium when the information recording apparatus records the record information onto the record medium. The second pre-pit signal detecting apparatus is provided with: a first detecting device such as a pre-pit signal detector etc., for detecting the pre-pit signal corresponding to a plurality of pre-pits on the basis of a gate signal to extract the pre-pit signal from the reproduction signal; a second detecting device such as a wobbling signal detector etc., for detecting a wobbling signal corresponding to a wobble of the wobbling track; a phase difference detecting device such as a gate position corrector etc., for detecting a phase difference between (i) the wobbling signal corresponding to the detected pre-pit signal and (ii) the detected pre-pit signal, for the wobbling signal in a plurality of cycles thereof; an averaging device such as a gate position corrector etc., for averaging the detected phase difference over the plurality of cycles of the wobbling signal; and a gate signal generating device such as a gate generator etc., for generating the gate signal on the basis of the averaged phase difference.
According to the second pre-pit signal detecting apparatus, since the phase difference between the detected wobbling signal and the detected pre-pit signal is averaged and then the gate signal for the detection of the pre-pit signal is generated on the basis of the averaged value, it is possible to generate the gate signal corresponding to the timing when the pre-pit signal is generated.
In one aspect of the second pre-pit signal detecting apparatus, the gate signal generating device generates the gate signal so that the averaged phase difference is coincident with a central timing of the gate signal.
By this, since the gate signal is generated so that the averaged phase difference is coincident with the central timing of the gate signal, such a possibility is more increased that the timing when the pre-pit signal is generated and the central timing of the gate signal are coincident with each other. Hence, it is possible to certainly detect the pre-pit signal even if the pulse width of the gate signal is narrowed.
Therefore, even if there is a change in the phase characteristic due to the temperature characteristic of the constitutional elements and the like (e.g., even if there is apparently generated a shift in the phase relationship between the wobbling signal and the pre-pit signal), since the gate signal can be generated such that the timing when the pre-pit signal is generated is coincident with the central timing of the gate signal, it is possible to reduce the detection leakage of the pre-pit signal.
The above object of the present invention can be also achieved by a first information recording apparatus for recording record information onto a record medium on which record control information for controlling a recording operation of the information recording apparatus is recorded in advance by forming a pre-pit on the record medium. The first information recording apparatus is provided with (A) the above described first pre-pit signal detecting apparatus of the present invention in various aspects, and (B) a recording device for recording the record information onto the record medium on the basis of the detected pre-pit signal.
According to the first information recording apparatus, since it is provided with the above described first pre-pit signal detecting apparatus of the present invention, it is possible to more accurately detect the pre-pit signal and accurately record the record information by more accurately obtaining the record control information.
The above object of the present invention can be also achieved by a second information recording apparatus for recording record information onto a record medium on which record control information for controlling a recording operation of the information recording apparatus is recorded in advance by forming a pre-pit and a wobbling track having a phase corresponding to the pre-pit on the record medium. The second information recording apparatus is provided with (A) the above described second pre-pit signal detecting apparatus of the present invention in various aspects, and (B) a recording device for recording the record information onto the record medium on the basis of the detected pre-pit signal.
According to the second information recording apparatus, since it is provided with the above described second pre-pit signal detecting apparatus of the present invention, it is possible to more accurately detect the pre-pit signal and accurately record the record information by more accurately obtaining the record control information.
The nature, utility, and further features of this invention will be more clearly apparent from the following detailed description with respect to preferred embodiments of the invention when read in conjunction with the accompanying drawings briefly described below.